Superconductivity and phase diagram of (Li0.8⁢Fe0.2)⁢OHFeSe1−?⁢S?

A series of $({\mathrm{Li}}_{0.8}{\mathrm{Fe}}_{0.2}){\mathrm{OHFeSe}}_{1\ensuremath{-}x}{\mathrm{S}}_{x}$ $(0\ensuremath{\le}x\ensuremath{\le}1)$ samples were successfully synthesized via hydrothermal reaction method and the phase diagram is established. Magnetic susceptibility suggests that an antiferromagnetism arising from $({\mathrm{Li}}_{0.8}{\mathrm{Fe}}_{0.2})\mathrm{OH}$ layers coexists with superconductivity, and the antiferromagnetic transition temperature nearly remains constant for various S doping levels. In addition, the lattice parameters of the both $a$ and $c$ axes decrease and the superconducting transition temperature ${T}_{c}$ is gradually suppressed with the substitution of S for Se, and eventually superconductivity vanishes at $x=0.90$. The decrease of ${T}_{c}$ could be attributed to the effect of chemical pressure induced by the smaller ionic size of S relative to that of Se, being consistent with the effect of hydrostatic pressure on $({\mathrm{Li}}_{0.8}{\mathrm{Fe}}_{0.2})\mathrm{OHFeSe}$. But the detailed investigation on the relationships between ${T}_{\mathrm{c}}$ and the crystallographic facts suggests a very different dependence of ${T}_{\mathrm{c}}$ on anion height from the Fe2 layer or $Ch\ensuremath{-}\mathrm{Fe}2\ensuremath{-}Ch$ angle from those in FeAs-based superconductors.